A control device 10 at a main center, in order for an update carried out in an operation database device M to be also conducted in an operation database device S at a sub-center, generates and transmits a differential log file 16 to a control device 20 at the sub-center. The control device 20 at the sub-center, when receiving a differential log file 22, updates the operation database device S on the basis of the log information in the differential log file 22, and accumulates the log information in a recovery log file 26. The log information of a recovery point set at the main center is incorporated into this recovery log file 26.